Thanks for the link, Daltxguy! All four greenhouse ideas are so interesting. The pit greenhouse design appealed to me the most. I like the idea of using the earth to insulate any walls that are not efficiently collecting sunlight. Having the structure partially in the earth also lowers its profile, potentially making it easier to blend into the landscape.

Using row covers inside of greenhouses is a technique that Eliot Coleman uses and describes in detail in his Four Season Harvest book.

-- "...I have nothing against authorities as such; I am only in favor of putting a question mark after just about everything they say." Ruth Stout

RFG – I think the pit greenhouse would work well on your site – you have a good south facing view and the yard slopes downwards.

I agree with you Joel – the geo-thermal one appealed to me as well, mainly because I have large trees all around in my current location, therefore get very little sun here in the winter, but the ground is still warm if you dig deep enough.

175ft is quite a bit of pipe to lay, but they had a large greenhouse. I don’t know how they came up with the length, but I’d like to know how to scale that idea.

-- Disobedience is the true foundation of liberty. The obedient must be slaves. - Thoreau

I can see where the length might have more to do with the temperature of the inflowing air than it does with square footage of the space being heated, though a smaller space would take less time to heat than a smaller one, etc…, and so they are related that way. I can see where there’s a whole lot of math involved, and I try to avoid that if I can. ;-)

-- "We are stardust. We are golden. And we've got to get ourselves back to the garden." Joni Mitchell

”I can see where there’s a whole lot of math involved”No doubt something involving triple integrals, markov chains, taking into account the Kondratiev long wave theory and keeping in mind the meissner effect.

-- Disobedience is the true foundation of liberty. The obedient must be slaves. - Thoreau